Method of constructing a medical needle holder assembly

ABSTRACT

A medical needle holder assembly comprising a generally tubular needle holder, a filter element constituted by a wad of a lengthy filament yarn of synthetic resin and a generally tubular filter retainer adapted to be received in the needle holder with the filter element fitted in the needle holder. The needle is manufactured by holding the needle holder and the filter retainer in positions longitudinally aligned with each other, positioning a predetermined length of filament yarn between the needle holder and the filter retainer, producing a unidirectional stream of air flowing away from the filament yarn thus positioned toward the foremost end of the filter retainer for moving the filament yarn onto the foremost end of the filter retainer, and moving the combination of the filter retainer and the filament yarn toward the needle holder, and forcing the filter retainer into the needle holder so that the filament yarn which has been in a loosely tangled condition is compacted into wad form within the needle holder.

The present invention relates to a needle holder assembly for use in amedical administering device or appliance such as a hypodermic syringeor a venoclysis equipment for introducing a liquid medicament ortransfusing blood into human body.

Extreme precautions are taken to prevent a pharmaceutical preparation orblood for transfusion from becoming contaminated with impurities beforethe preparation or blood is injected into the human body. Actually,however, there still exist various possibilities that impurities arepresent in or admixed to the preparation or blood before and even duringthe administering process. Impurities may happen to be introduced into aliquid medicament when, for example, an ampoule or other breakablecontainer storing the preparation is punctured prior to injection orwhen a fluid conducting tube is being fitted to the rubber plug of thereservoir of a venoclysis equipment. The fine fragments of the puncturedcontainer or the fine particles of rubber scraped off from the plug ofthe venolysis equipment may find their way through the administeringsystem into the blood stream of the human body and may thus injure thevascular tissues.

A variety of filter media have therefore been developed and have foundpractical applications for the purpose of removing impurities fromliquid medicaments and blood for transfusion before the medicaments orblood are discharged from the needles or canulae of the administeringdevices. One of the typical examples of the prior art filter mediaadapted to achieve this purpose is formed of staple fibers which arepressed or otherwise compacted into lump form and another example isformed of nylon fabrics or a mass of sintered nylon powder. The filterelement is usually fitted into the passageway in the needle holder andcollects impurities when the liquid medicament or blood for transfusionis passed through the filter element toward the needle. When the filterelement is thus subjected to the stream of the medicament or bloodpassing therethrough, it frequently happens that relatively short fibersor the fragments of fibers are separated from the lump of the compactedstaple fibers or the fabrics of nylon or fine gragments are fractured ortorn apart from the mass of the sintered nylon powder. This not onlyresults in deterioration of the collection efficiency of the filterelement being used but is causative of production of additionalimpurities (herein called "secondary impurities") although the majorityof the impurities (herein called "primary impurities") initiallycontained in the medicament or blood directed into the needle holder maybe collected by the filter element. The filter element thus provides initself another source of impurities and loses in significance as thefilter means.

With a view to solving these problems, I, the inventor, have proposed anew filter element in a medical needle assembly as disclosed in U.S.Pat. No. 3,859,999 dated Jan. 14, 1975 and assigned to IshikawaManufacturing Company, Limited, Tokyo, Japan. The filter element shownin this issued patent comprises a wad of at least one length ofcontinuous filament of synthetic resin substantially uniformly entwinedinto wad form and is preferably located at the foremost end of thelongitudinal passageway in a needle holder. In the course of themanufacture of such needle assemblies on a commercial basis, however, ithas been found that difficulties are encountered in accurately locatingthe filter element in the needle holder and fixedly holding the filterelement in position within the needle holder. This is partly because ofthe extremely small space available in the needle holder and partlybecause of the inherently shapeless configuration of the filter elementcomposed of the wad of an entwined filament. If the filter element islocated out of a predetermined position relative to the needle holder ordislodged from the predetermined position, the filter element causesobstruction when the needle assembly is being fitted to a syringe barrelor an adapter of a venoclysis equipment. The present inventioncontemplates provision of a method of manufacturing a medical needleholder assembly which is free from such a problem encountered in theapplicant's previously proposed needle assembly as well as the problemsinherent in needle holder assemblies using other prior art filterelements of the natures hereinbefore described.

It is, therefore, an important object of the present invention toprovide an improved medical needle holder assembly having a filterelement which is capable of removing impurities, viz., primaryimpurities from a liquid medicament or blood to be discharged from theneedle holder assembly and which will not form a source of secondaryimpurities during use.

It is another important object of the invention to provide an improvedmedical needle holder assembly having a filter element which held inposition within the needle holder assembly during transportation,storage and use.

It is still another important object of the present invention to providea method of assembling together a needle holder, a filter element and afilter retainer so as to obtain such an improved needle holder assembly.

It is still another important object of the invention to provideapparatus adapted to put the method into practice on a commercial basis.

In accordance with an outstanding aspect of the present invention, thereis provided a method of assembling together a generally tubular needleholder, a filter element composed of a wad of a predetermined length offilament yarn of synthetic resin and a generally tubular filter retaineradapted to be received in the needle holder with the filter elementfitted in the needle holder, comprising (1) feeding the needle holderand the filter element into respective predetermined positionslongitudinally spaced apart from and aligned with each other and feedingthe filament yarn into a predetermined position intermediate between thepredetermined positions of the needle holder and the filter retainer,(2) producing a unidirectional stream of air flowing from thepredetermined position of the filament yarn toward the predeterminedposition of the filter retainer for moving the filament yarn from thepredetermined position thereof toward the filter retainer in thepredetermined position thereof until the filament yarn is forced in theform of a tangle against the foremost end of the filter retainer, (3)moving the filter retainer from the predetermined position thereoftoward the needle holder in the predetermined position thereof with thetangle of the filament yarn carried on the foremost end of the filterretainer, and (4) forcing the filter retainer into the needle holder inthe predetermined position thereof so that the tangle of the filamentyarn is compacted into wad form within the needle holder. The method mayfurther comprise subjecting the filament yarn to a predetermined tensilepull, scraping the filament yarn against a sharpened edge while applyingthe tensile pull to the yarn for elastically elongating the yarn, andreleasing the filament yarn from the tensile pull for allowing the yarnto longitudinally shrink before the filament yarn is fed into thepredetermined position thereof. The respective predetermined positionsof the needle holder and the filter retainer are preferably aligned witheach other horizontally. The unidirectional stream of air to move thefilament yarn onto the foremost end of the filter retainer may beproduced preferably by developing a suction behind the filter retainerin the predetermined position thereof so that a differential pressure iscreated between the predetermined position of the filament yarn and thefilter retainer.

In accordance with another outstanding aspect of the present invention,there is provided an apparatus for assembling together the abovementioned needle holder, filter element and filter retainer, comprising(1) an elongated hollow transport tube having a longitudinal passagewaywhich is open at its foremost end and having formed in its intermediateportion an opening which is sized to permit the filament yarn to passtherethrough, (2) first feeding and positioning means for feeding theneedle holder in each cycle of operation into a predetermined positionlongitudinally aligned with the longitudinal passageway in the transporttube and having its rearmost end located at the open foremost end of thelongitudinal passageway, (3) second feeding and positioning means forfeeding the filter retainer in each cycle of operation into apredetermined position within the longitudinal passageway in thetransport tube, the predetermined position of the filter retainer beinglongitudinally spaced apart and aligned with the predetermined positionof the needle holder across the intermediate portion of the longitudinalpassageway, (4) third feeding and positioning means for feeding thefilament yarn in each cycle of operation into a predetermined positionin the intermediate portion of the longitudinal passageway of thetransport tube through the opening formed in the intermediate portion,(5) pneumatic transfer means for producing in the longitudinalpassageway in the transport tube a unidirectional stream of air flowingfrom the intermediate portion toward the predetermined position of thefilter retainer for moving the filament yarn from the predeterminedposition thereof toward the filter retainer in the predeterminedposition thereof until the filter element is forced in the form of atangle against the foremost end of the filter retainer, and (6) drivemeans for moving the filter retainer from the predetermined positionthereof toward the needle holder in the predetermined position thereofwith the tangle of the filament yarn carried on the foremost end of thefilter retainer and forcing the filter retainer into the needle holderin the predetermined position thereof so that the tangle of the filamentyarn is compacted into wad form within the needle holder.

The needle holder assembly thus obtained in accordance with the presentinvention comprises, in combination, a generally tubular needle holderhaving a hollow body portion formed with an annular foremost end wall, agenerally tubular filter retainer received in the body portion andhaving an apertured foremost end wall spaced apart from the annularforemost end wall of the body portion of the needle holder, and a filterelement which is composed of a wad of a single lengthy filament yarn ofsynthetic resin and which is positioned between the annular foremost endwall of the body portion of the needle holder and the apertured foremostend of the filter retainer.

The method according to the present invention will become more apparentfrom the following description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a longitudinal sectional view of a medical needle holderassembly which can be obtained according to the present invention;

FIGS. 2a, 2b and 2c are plan views each of which show a preferredexample of the pattern of the apertures formed in the foremost end wallof the filter retainer incorporated in the needle holder assemblyillustrated in FIG. 1;

FIG. 3 is a perspective view of an arrangement which forms part of anapparatus adapted to carry out the method according to the presentinvention;

FIG. 4 is a longitudinal sectional view showing part of the arrangementillustrated in FIG. 3 in one stage of operation;

FIG. 5 is a longitudinal sectional view showing, to an enlarged scale,part of the arrangement illustrated in FIG. 3 in another stage ofoperation; and

FIG. 6 is a longitudinal sectional view showing, also to an enlargedscale, part of the arrangement illustrated in FIG. 3 in still anotherstage of operation.

Referring to FIG. 1, a needle holder assembly comprises a needle holder10 which consists of a forwardly tapered hollow body portion 12 havingan annular end wall 14 at its reduced foremost end and a cylindricalextension 16 projecting forward from the annular end wall 14 of the bodyportion 12 and having a longitudinal passageway 18 which is open at theforemost end of the extension 16. The body portion 12 is formed with agenerally frustoconical cavity 20 which is open at the enlarged rearmostend of the body portion 12 and which communicates at the opposite end ofthe body portion 12 with the longitudinal passageway 18 in thecylindrical extension 16. A filter element 22 composed of a wad of asingle lengthy filament yarn of synthetic resin is located in theforemost end portion of the frusto-conical cavity 20 in the body portion12 of the needle holder 10 thus constructed and is held in position bymeans of a forwardly tapered hollow filter retainer 24. The filterretainer 24 has a generally frusto-conical outer peripheral surfacewhich is shaped conformingly to part of the inner peripheral surface ofthe body portion 12 of the needle holder 10. The filter retainer 24 isclosely fitted into the main body portion 12 of the needle holder 10 insuch a manner that the reduced foremost end thereof is spaced apart apredetermined distance from the inner face of the annular end wall 14 ofthe body portion 12 in longitudinal direction of the retainer 24 andthat the enlarged rearmost end thereof is substantially flush with theenlarged rearmost end of the body portion 12 of the needle holder 10.The outside diameter of the rearmost end of the filter retainer 24 isthus substantially equal to the inside diameter of the rearmost end ofthe body portion 12 of the needle holder 10, as denoted by d in FIG. 1.The filter retainer 24 has a longitudinal passageway 26 fully open atthe enlarged rearmost end of the retainer 24 and has formed at itsreduced foremost end an end wall 28 which is formed with a plurality ofapertures 30. The apertures 30 are preferably arranged substantiallysymmetrically with respect to the center axis of the end wall 28 anduniformly distributed in the foremost end wall 28 with a suitablepattern. FIGS. 2a, 2b and 2c illustrate preferred examples of thepattern with which the apertures 30 may be arranged in the end wall 28of the filter retainer 24. In the arrangement shown in FIG. 2a, the endwall 28 of the filter retainer is made up of a circular rim portion 32and a plurality of radial portions 34 which are substantiallyequiangularly spaced apart from each other about the center axis of theend wall 28. The radial portions 34 extend spokewise inwardly from therim portion 32 and meet each other at the center axis of the end wall 28so that the individual apertures 30 have generally sectorial formshaving substantially equal central angles about the center axis of theend wall 28. The radial portions 34 are herein shown as being three innumber so that each of the sectorial apertures 30 is assumed to have acentral angle of approximately 120 degrees about the center axis of theend wall 28 but it is apparent that the number of the radial portions 34may be selected arbitarily depending upon the specific designconsiderations to be given to the needle holder assembly. The end wall28 shown in FIG. 2b is in the form of a grille having a number ofinterstices which form the apertures 30. These apertures 30 are shown tobe formed by crossings intersecting at right angles but, if desired, thecrossings may be arranged in such a manner as to intersect each other atother angles insofar as the apertures 30 are distributed approximatelyuniformly in the end wall 28. In the end wall 28 shown in FIG. 2c, oneof the apertures 30 is located substantially centrally of the end wall28 and the others are arranged around the central aperture preferablysymmetrically with respect to the center axis of the end wall 28. Thecentral aperture is shown to be larger in diameter than the others butit is apparent that the respective diameters of the individual apertures30 arranged as shown in FIG. 2c may be selected arbitarily.

Turning back to FIG. 1, the filter retainer 24 having the aperturedforemost end wall 28 thus arranged terminates longitudinally halfway ofthe frusto-conical cavity 20 in the body portion 12 of the needle holder10 so that the filter element 20 formed of a wad having an inherentlyshapeless configuration is stuffed between the inner face of thepreviously mentioned annular end wall 14 of the body portion 12 of theneedle holder 10 and the outer face of the apertured foremost end wall28 of the filter retainer 24. The relation between the length of thecavity 20 in the body portion 12 of the needle holder 10 and the lengthof the filter retainer 24, viz., the size of the space to accommodatethe filter element 22 should therefore be selected depending upon thedesired density or, more exactly, the percent of voidness of the filterelement 22.

With the filter element 22 and the filter retainer 24 thus fitted intothe needle holder 10, communication is provided between the longitudinalpassageway 26 in the filter retainer 24 and the longitudinal passageway18 in the cylindrical extension 16 of the needle holder 10 through theapertures 30 in the foremost end wall 28 of the filter retainer 24 andthe interstices in the filter element 22. A piercing needle is fitted tothe cylindrical extension 16 of the needle holder 10 as is customary inthe art whilst the filter retainer 24 is fitted to the syringe barrel ofa hypodermic syringe or to the adapter of a venoclysis equipment, thoughnot shown in the drawings.

Similarly to the filter medium incorporated into the medical needleassembly disclosed in the previously named U.S. Pat. No. 3,859,999, thefilament yarn constituting the filter element 22 preferably has a deniernumber within the range of from about 75 to about 150 or, morepreferably, from about 75 to about 85 and is stuffed into the needleholder 10 to form a wad which preferably has a density within the rangeof from about 0.8 gram/cm³ to about 1.6 gram/cm³ or, more preferably,from about 0.8 gram/cm³ to about 0.9 gram/cm³. Such a filament yarn maybe either a monofilament yarn composed of a single lengthy filament or amultifilament yarn composed of a plurality of spun lengthy filaments. Ineither case, the filament or each of the filaments should be produced byextruding a continuous filament from an orifice in a plastics extrusiondie (not shown) which is well known in the art and cutting thecontinuous filament to a predetermined length after the extrudedfilament is set. The filament produced in this manner is devoid of andfree from the possibility of forming short fibers and, for this reason,there is not any fear that the filter element 22 constituted by such afilament or filaments should produce secondary impurities in the dosagesolution or blood which is passed through the filter element during useof the needle assembly. For the reason which will be clarified later,furthermore, a multifilament yarn is preferable to a monofilament yarnas the material to form the filter element 22.

FIG. 3 illustrates an arrangement forming part of an apparatus adaptedto carry out the method according to the present invention for easilyand accurately assembling together the needle holder 10, the filterelement 22 and the filter retainer 24 of the natures thus far describedwith reference to FIG. 1.

The arrangement shown in FIG. 3 comprises an elongated, horizontalhollow transport tube 36 and first, second and third feeding andpositioning means 38, 40 and 42 which are respectively operative toconvey the above mentioned needle holder, filter retainer and filamentyarn into predetermined positions relative to the transport tube 36 ineach cycle of operation. As is better seen in FIG. 4, the transport tube36 is formed with a longitudinal passageway 44 extending throughout thelength of the tube 36 and having open foremost and rearmost ends 46 and48. The transport tube 36 is further formed with an opening 50 in thetop wall of its intermediate portion for the purpose of admitting afilament yarn into the tube 36 as will be described later. The transporttube 36 is preferably provided with a guide tube 52 having a passageway54 extending upwardly from the above mentioned opening 50 in thetransport tube 36 and terminating at the upper end of the guide tube 52.

In the vicinity of the foremost end of the transport tube 36 thusarranged is located a magazine 56 which forms part of the abovementioned first feeding and positioning means 38. As will be better seenfrom FIG. 4, the magazine 56 has front and rear vertical walls 58 and 60so as to form therebetween a vertical chamber 62 which is generallyperpendicular to the direction in which the transport tube 36 extends.The magazine 56 has a circular opening 64 formed in a lower end portionof its rear vertical wall 60 and the transport tube 36 has its foremostend fixedly connected to or, as shown, innegral with the rear verticalwall 60 of the magazine 56 so that the longitudinal passageway 44 in thetransport tube 36 has its foremost open end 46 contiguous to thelowermost portion of the vertical chamber 62 through the opening 64 inthe rear vertical wall 60 of the magazine 56. The magazine 56 thusconstructed is adapted to have accomodated in the vertical chamber 62thereof a stack of needle holders 10 each having the configurationillustrated in FIG. 1. The needle holders 10 are stacked upon oneanother in vertical direction within the vertical chamber 62 so that theone located at the bottom of the vertical chamber 62 is substantially inline with the longitudinal passageway 44 in the transport tube 36 andhas its open rearmost end located in close proximity to the circularopening 64 in the rear vertical wall 60 of the magazine 56. The frontand rear vertical walls 58 and 60 of the magazine 56 are spaced apart adistance which is substantially equal to the overall length of theneedle holders 10 thus positioned within the chamber 62 so that each ofthe needle holders 10 above the one located at the bottom of thevertical chamber 62 of the magazine 56 has its foremost and rearmostends in slidable contact with the inner faces of the front and rearvertical walls 58 and 60, respectively. The circular opening 64 in therear vertical wall 60 of the magazine 56 has a diameter which issubstantially equal to the inside diameter of the transport tube 36 asdenoted by D in FIG. 4. The diameter D is substantially equal to theinside diameter d of the enlarged open rearmost end of each needleholder 10. The needle holder 10 located at the bottom of the verticalchamber 62 therefore has its rearmost end in contact with the circularedge portion of the rear vertical wall 60 formed with the opening 64 andits foremost end in contact with the inner face of the front verticalwall 58 of the magazine 56.

Though not shown, the first feeding and positioning means furthercomprise a holder feed mechanism operative in predetermined cycles todownwardly convey the needle holders 10 within the vertical chamber 62in the magazine 56 successively into the bottom portion of the chamber62, vix., a position aligned with the longitudinal passageway 44 in thetransport tube 36 through the circular opening 64 in the rear verticalwall 60 of the magazine 56 and to withdraw completed needle holderassemblies successively from the bottom portion of the chamber 62. Theconstruction of such a mechanism is a mere matter of design choice andis not herein illustrated.

As is also seen in FIG. 4, the transport tube 36 further has an opening66 formed in the top wall of its portion in the neighbourhood of therearmost end thereof and carried on the particular portion a magazine 68which forms part of the second feeding and positioning means 40previously mentioned with respect to the arrangement illustrated in FIG.3. The magazine 68 has front and rear vertical walls 70 and 72 which arespaced apart in parallel from each other so as to form therebetween avertical chamber 74. The front and rear vertical walls 70 and 72 havetheir respective lower ends fixedly connected to or, as shown, integralwith the top wall of the transport tube 36 so that the vertical chamber74 in the magazine 68 is open at its lower end to the longitudinalpassageway 44 in the transport tube 36 through the opening 66. Themagazine 68 thus constructed is adapted to have accommodated within thevertical chamber 74 thereof a stack of filter retainers 24 each havingthe configuration illustrated in FIG. 1. The filter retainers 24 arestacked upon one another in vertical direction within the chamber 74 sothat the lowermost one of the filter retainers is positioned within thelongitudinal passageway 44 in the transport tube 36 with its reducedforemost end directed toward the foremost end 46 of the passageway 44and its enlarged rearmost end located at a predetermined distance fromthe rearmost end of the passageway 44 as shown. Since, in this instance,the outside diameter d of the enlarged rearmost end of each filterretainer 24 is substantially equal to the inside diameter D of thetransport tube 36 as will be understood from the foregoing description,the filter retainer 24 positioned in the transport tube 36 islongitudinally slidable in the passageway 44 in the transport tube 36.Though not shown in the drawings, the second feeding and positioningmeans of the apparatus embodying the present invention further comprisea retainer feed mechanism operative to downwardly move the filterretainers 24 successively into the longitudinal passageway 44 in thetransport tube 36 in predetermined cycles which are substantiallysynchronized with the cycles in which the needle holders 10 in themagazine 56 of the first feeding and positioning means are moveddownwardly in the vertical chamber 62 of the magazine 56. Theconstruction of such a mechanism is merely a matter of design choice forthose skilled in the art and is not herein shown, as in the case of theholder feed mechanism forming part of the first feeding and positioningmeans.

Turning back to FIG. 3, the third feeding and positioning means 42 isintended to feed a continuous filament yarn 76 from any suitable sourcesuch as a yarn package 78 supported on a creel (not shown). If desired,the filament yarn 76 may be supplied directly from an extrusion dieproducing a monofilament or a spinning process producing a multifilamentyarn, though not shown in the drawings. The yarn 76 from whatever sourceis supplied, is passed through a tensioning roller 80 to a stationaryknife-edged member 82 serving as scraping means for the yarn 76 as willbe described in details. The knife-edged member 82 has a sharpenedhorizontal edge which is preferably located over the upper end of thepreviously described guide tube 52 on the transport tube 36 as shown.Below the knife-edged member 82 are positioned a pair of feed rollers 84and 84' which are in rolling contact with each other over the upper endof the above mentioned guide tube 52. One of the feed rollers 84 and 84'is driven for rotation about its axis by suitable drive means such as anelectric motor (not shown) so that the filament yarn 76 from the supplypackage 78 is continuously passed between the feed rollers 84 and 84' ata predetermined rate and is inserted into the vertical passageway 54 inthe guide tube 52. Immediately above the upper end of the guide tube 52are positioned suitable cutting means such as for example a pair ofknives 86 and 86'. The knives 86 and 86' are operatively connected tosuitable actuating means (not shown) adapted to measure the length ofthe filament yarn 76 passed between the feed rollers 84 and 84' oradmitted into the guide tube 52 and to actuate the knives 86 and 86' tocut the yarn 76 in a predetermined length during each of cycles whichare synchronized with the cycles in which the needle holders 10 in themagazine 56 of the first feeding and positioning means and the filterretainers 24 in the magazine 68 of the second feeding and positioningmeans are successively moved into respective positions aligned with eachother through the longitudinal passageway 44 in the transport tube 36(see FIG. 4). A segment of filament yarn with the predetermined lengthis in this manner inserted into the guide tube 52 in each cycle ofoperation. As illustrated in FIG. 4, the segment of the filament yarn 76thus inserted into the guide tube 52 collects in the longitudinalpassageway 44 in the transport tube 36 below the opening 50 by reason ofthe gravity thereof and is loosely entwined into the form of a tangle88. The tangle 88 of the filament yarn is temporarily detained in theintermediate portion of the longitudinal passageway 44 in the transporttube 36. The guide tube 52 is herein assumed to form part of the thirdfeeding and positioning means although such a tube may be dispensed withif desired.

A cylindrical piston 90 is longitudinally slidable through thelongitudinal passageway 44 in the transport tube 36 between a firstposition having its foremost end substantially flush with the inner faceof the rear vertical wall 72 of the magazine 68 as seen in FIGS. 4 and 5and a second position having the foremost end located at the foremostend 46 of the longitudinal passageway 44 as seen in FIG. 6. The piston90 has its rearmost end fixedly connected to or, as shown, integral witha connecting rod 92 which is in turn connected to a suitable mechanicaldriving source (not shown). The driving source is adapted to move thepiston 90 forwardly from the first position to the second positionthereof and thereafter backwardly from the second position to the firstposition thereof during each of the cycles of operation. The piston 90is formed with a cylindrical cavity 94 which is open at the foremost endof the piston 90 and closed at the rearmost end of the piston 90. Thepiston 90 has further formed in its peripheral wall an aperture 96(FIGS. 5 and 6) which is open to the cavity 94. In consonance with theaperture 96 thus provided in the piston 90, the transport tube 36 isformed with a vent 98 (shown by dotted lines in FIGS. 3 and 4) which isso located as to be in alignment with the aperture 96 in the piston 90when the piston 90 is in the previously mentioned first position thereofas seen in FIGS. 4 and 5. The vent 98 in the transport tube 36 is incommunication with a source (not shown) of suction or a partial vacuumby way of a suction pipe 100 connected to the transport tube 36 asillustrated in FIG. 3. When the piston 90 is in the first positionthereof and simultaneously the filter retainer 24 is positioned withinthe transport tube 39 with its rearmost end engaged by the foremost endof the piston 90 as seen in FIGS. 4 and 5, communication is establishedbetween the longitudinal passageway 44 in the transport tube 36 and thesource of suction through the apertures 30 in the foremost end wall 28of the filter retainer 24, the longitudinal passageway 26 in the filterretainer 24, the cavity 94 and the aperture 96 in the piston 90, thevent 98 in the transport tube 36 and the passageway (not shown) in thesuction pipe 98. When a suction is thus developed in the transport tube36 with the upper end of the guide tube 52 open to the atmosphere, thereis created a differential pressure between the intermediate portion ofthe longitudinal passageway 44 and the vent 98 in the transport tube 36so that a unidirectional stream of air is produced away from theintermediate portion of the longitudinal passageway 44 toward theforemost end of the filter retainer 24 positioned ahead of the piston90. As an alternative to the suction thus built up in the transport tube36, air under pressure may be ejected into the longitudinal passageway44 in the transport tube 36 in a direction reverse to the direction ofthe suction so as to produce an essentially similar stream of air in thepassageway 44.

The operation of the apparatus thus constructed and arranged will now bedescribed with concurrent reference to FIGS. 3 to 6. Throughout theperiod of operation, one of the feed rollers 84 and 84' (FIG. 3) is keptdriven by suitable drive means (not shown) so that the filament yarn 76is continuously fed from the yarn package 78 at a fixed rate through thetensioning roller 80 and the stationary knife-edged member 82 and issubjected to a tensile pull which is maintained substantially constantby means of the tensioning roller 80. When the filament yarn 76 ispassed through the knife-edged member 82, the yarn 76 is scraped againstthe sharpened horizontal edge of the knife-edged member 82 and, as aconsequence, the filament or each of the filaments of synthetic resinconstituting the yarn 76 is elastically elongated or drawn because theyarn 76 is maintained taut between the knife-edged member 82 and thefeed rollers 84 and 84' by means of the tensioning roller 80 which ispositioned between the yarn package 78 and the knife-edged member 80. Itis, in this instance, important that the tensioning roller 80 be soconditioned as not to produce an overstrain in the filament yarn 76 forthe purpose of preventing the filament yarn 76 from being cut at thesharpened edge of the knife-edged member 82 or between the knife-edgedmember 82 and the feed rollers 84 and 84'. When the filament yarn 76which is elastically elongated or drawn in this fashion is freed fromthe tension at a subsequent stage of process, the yarn 76 is allowed toshrink longitudinally and becomes curled throughout its length with theresult that the yarn 76 is enabled to intricately entwine on itself andto form a uniformly dense filter element at a further subsequent stage.To enable the knife-edged member 82 to effectively scrape the filamentyarn 76, it is advisable that the sharpened horizontal edge of theknife-edged member 82 be located vertically in alignment with the upperend of the guide tube 52 on the horizontal transport tube 36 aspreviously noted.

The filament yarn 76 which has passed through the feed rollers 84 and84' is downwardly fed and inserted into the vertical passageway 54 inthe guide tube 52. When the filament yarn 76 thus admitted into theguide tube 52 reaches a predetermined length, the knives 86 and 86'positioned in proximity to the upper end of the guide tube 52 areactuated to cut the yarn 76 into a segment having the predeterminedlength. The segment of the filament yarn 76 falls through the verticalpassageway 54 in the guide tube 52 and collects within the intermediateportion of the longitudinal passageway 44 in the horizontal transporttube 36 as seen in FIG. 4. The segment of the filament yarn, which isnow longitudinally shrunk and curled as above noted, is loosely entwinedinto the form of a tangle 88 and is temporarily detained within theintermediate portion of the longitudinal passageway 44 in the transporttube 36. The knives 86 and 86' are actuated in predetermined cycles sothat the segment of the filament yarn having the predetermined length issupplied to the transport tube 36 in each of the cycles.

While the segment of the filament yarn 76 is thus being fed into thetransport tube 36 by the third feeding and positioning means 38 in eachcycle of operation, the holder feed mechanism forming part of the firstfeeding and positioning means 38 and the retainer feed mechanism formingpart of the second feeding and positioning means 40 are initiated,either concurrently or at different timings, into action to downwardlymove the needle holders 10 within the vertical chamber 62 in themagazine 56 and to downwardly move the filter retainers 24 in thevertical chamber 74 of the magazine 68. The lowermost one of the stackof needle holders 10 within the vertical chamber 62 in the magazine 56is thus positioned at the bottom of the chamber 62 and is thus alignedwith the longitudinal passageway 44 in the transport tube 36 and thelowermost one of the filter retainers 24 in the vertical chamber 74 ofthe magazine 68 is fed into the longitudinal passageway 44 in thetransport tube 36 and is aligned with the needle holder 10 positionedahead of the foremost end 46 of the longitudinal passageway 44, as seenin FIG. 4. When the lowermost one of the stack of the filter retainers24 is positioned in the longitudinal passageway 44 in the transport tube36, the piston 90 is held in its first position having the foremost endin contact with the enlarged open rearmost end of the particular filterretainer 25 and having the aperture 96 aligned with the vent 98 in thetransport tube 36 as will be seen from FIGS. 4 and 5. A suction is thendeveloped in the passageway in the suction pipe 100 (FIG. 3) so that aunidirectional stream of air is produced in the longitudinal passageway44 in the transport tube 36. The stream of air flows from theintermediate portion of the passageway 44 toward the piston 90 behindthe filter retainer 24 in the passageway 24 and urges the tangle 88 ofthe filament yarn toward the filter retainer 24 in the passageway 44.The tangle 88 of the filament yarn is consequently moved onto theforemost end of the filter retainer 24 in the passageway 44 and isforced against the outer face of the apertured foremost end wall 28 ofthe particular filter retainer 24 as seen in FIG. 5. The stream of airpast the interstices in the tangle 88 of the filament yarn thus forcedagainst the forward end face of the filter retainer 24 is directed intothe suction pipe 100 through the apertures 30 in the foremost end wall28 and the longitudinal passageway 26 of the filter retainer 24, thecavity 94 and the aperture 96 in the piston 90 and the vent 98 in thetransport tube 36 in this sequence. When the tangle 88 of the filamentyarn reaches the foremost end of the filter retainer 24 in thelongitudinal passageway 44 in the transport tube 36, then the supply ofsuction is interrupted and, in turn, the drive means for the piston 90is actuated to move the piston 90 forwardly in the longitudinalpassageway 44 from its first position illustrated in FIG. 5. As thepiston 90 is thus moved forward from the first position thereof, thefilter retainer 24 contacting the foremost end of the piston 90 and thetangle 88 of the filament yarn contacting the foremost end face of theretainer element 24 are also moved forward in the longitudinalpassageway 44 in the transport tube 36. When the piston 90 reaches itssecond position having the foremost end located at the foremost end 46of the longitudinal passageway 44, the filter retainer 24 is positionedimmediately ahead of the foremost end 46 of the passageway 44 in thetransport tube 36 and is received into the body portion 12 of the needleholder 10 positioned at the bottom of the vertical chamber 62 in themagazine 56 as seen in FIG. 6. The filter retainer 24 thus fitted to theneedle holder 10 has its foremost end wall 28 spaced apart from theannular end wall 14 of the body portion 12 of the needle holder 10 sothat the tangle 88 of the filament yarn at the foremost end of thefilter retainer 24 is received between the outer face of the aperturedforemost end wall 28 of the filter retainer 24 and the inner face of theannular end wall 14 of the main body portion 12 of the needle holder 10.The tangle 88 of the filament yarn is consequently compacted into theform of a wad constituting a filter element 22. When the filter retainer24 is forced into the body portion 12 of the needle holder 10, theneedle holder 10 is forced at the foremost end of its cylindricalextension 16 against the inner face of the front vertical wall 58 of themagazine 56 and is securely held in position relative to the magazine sothat the filter retainer 24 can be closely and accurately fitted to theneedle holder 10. A needle assembly is now complete with the needleholder 10 and the filter retainer 24 fitted to each other with thefilter element 22 held in position within the longitudinal passageway 20of the needle holder 10 as is better seen in FIG. 1. The holder feedmechanism forming part of the first feeding and positioning means 38(FIG. 3) is then actuated to withdraw the complete needle assembly fromthe chamber 62 in the magazine 56 and to further move the stack of theneedle holder 10 downwardly in the chamber 62 so that another needleholder 10 is positioned at the bottom of the chamber 62. On the otherhand, the piston 90 is moved back from its second position shown in FIG.6 to its first position shown in FIG. 5 by the action of the drive meansassociated with the connecting rod 92 for the piston 90 or by a springaction constantly biasing the connecting rod 92 to move the piston 92toward the first position thereof. When the piston 90 is thus retractedinto its first position close to the rearmost end 48 of the longitudinalpassageway 44 in the transport tube 36, then the retainer feed mechanismforming part of the second feeding and positioning means 40 (FIG. 3) isactuated to further move the stack of the filter retainers 24 downwardlyin the vertical chamber 74 of the magazine 68 so that another filterretainer 24 is moved into the longitudinal passageway 44 in thetransport tube 36. By this time, a second segment of filament yarn iscollected in the form of a tangle 88 within the intermediate portion ofthe transport tube 36 and is ready to be moved onto the foremost end ofthe filament retainer 24 by a suction to be developed in the suctionpipe 100. Medical needle assemblies each having the configurationillustrated in FIG. 1 are in this fashion completed through repetitionof the steps thus far described with reference to FIGS. 3 to 6.

From the foregoing description it will be appreciated that the presentinvention provides the following major advantages:

1. Because of the fact that the filter element 22 is constituted by asingle filament yarn of synthetic resin, the filter element 22 will notform a source of secondary impurities that would otherwise contaminatethe liquid medicament or blood which has been cleared of primaryimpurities. For the same reason, the filtration ability and efficiencyof the filter element 22 can be easily and accurately controlled byselecting the length and/or the thickness of the filament yarn.

2. Because the filament yarn in a tangled condition is pressed into theneedle holder 10 with the aid of the filter retainer which is externallyshaped conformingly to the external peripheral surface of the bodyportion 12 of the former and because the needle holder 10 and the filterretainer 24 are longitudinally held in strict alignment with each otherwhen being assembled together, the tangle 88 of the filament yarn can beeasily and accurately fitted to the needle holder 10 simply byreciprocating motions of the piston 90 in the transport tube 36.

3. Because the filament yarn 76 to form the filter element 22 is onceelongated under tension and is allowed to shrink when released from thetension, the cut segment of the filament yarn has an enhanced tendencyto curl and entwine on itself so that the filter element 22 constitutedby the wad of the resultant filament yarn has a uniform density or, inother words, interstices which are distributed uniformly throughout thewad.

4. The external geometry of the filter retainer 24 and accordingly theinternal space of the needle holder 10 can be selected without respectto the size of the syringe barrel of a hypodermic syringe or the adapterof a venoclysis equipment to which the needle holder assembly is to befitted. This means that the space to accommodate the filter element 22within the needle holder 10 can be selected irrespective of the size ofthe syringe barrel or the adapter of the venoclysis equipment.

5. Because of the fact that the filter element 22 is held in positionwithin the needle holder 10 by means of the filter retainer 24 which isclosely fitted to the needle holder 10 and which thus forms part of theneedle holder assembly, the filter element 22 will not constitute anobstacle when the needle holder assembly is being fitted to a syringebarrel or an adapter of a venoclysis equipment.

While a few embodiments of the medical needle holder assembly and onlyone embodiment of the apparatus according to the present invention havebeen described with reference to the accompanying drawings, it should beborne in mind that such are not limitative of the present invention andmay therefore be changed and modified if desired without departing fromthe spirit and scope of the present invention.

What is claimed is:
 1. A method of assembling together a generallytubular needle holder, a filter element composed of a wad of apredetermined length of filament yarn of synthetic resin and a generallytubular filter retainer adapted to be received in said needle holderwith said filter element fitted in the needle holder, comprising (1)feeding said needle holder and said filter retainer into respectivepredetermined positions longitudinally spaced apart from and alignedwith each other and feeding said filament yarn into a predeterminedposition intermediate between said predetermined positions of saidneedle holder and said filter retainer, (2) producing a unidirectionalstream of air flowing from said predetermined position of said filamentyarn toward said predetermined position of said filter retainer formoving the filament yarn from said predetermined position thereof towardthe filter retainer in said predetermined position thereof until thefilament yarn is forced in the form of a tangle against the foremost endof said filter retainer, (3) moving said filter retainer from saidpredetermined position thereof toward said needle holder in saidpredetermined position thereof with said tangle of said filament yarncarried on the foremost end of said filter retainer, and (4) forcing thefilter retainer into said needle holder in said predetermined positionthereof so that the tangle of the filament yarn is compacted into wadform within said needle holder.
 2. A method as defined in claim 1,further comprising subjecting said filament yarn to a predeterminedtensile pull, scraping the filament yarn against a sharpened edge whileapplying the tensile pull to the yarn for elastically elongating theyarn, and releasing the filament yarn from said tensile pull forallowing the yarn to longitudinally shrink before the filament yarn isfed into said predetermined position thereof.
 3. A method as set forthin claim 1, in which said predetermined positions of said needle holderand said filter retainer are horizontally aligned with each other.
 4. Amethod as set forth in claim 3, in which said filament yarn isdownwardly conveyed over said predetermined position thereof and isallowed to fall into the predetermined position thereof.
 5. A method asset forth in claim 3, in which each of said needle holder and saidfilter retainer is downwardly conveyed into said predetermined positionthereof in a substantially vertical path.
 6. A method as set forth inclaim 1, in which said unidirectional stream of air is produced bydeveloping a suction behind said filter retainer in said predeterminedposition thereof so that a differential pressure is created between saidpredetermined positions of said filament yarn and said filter retainer.